Preformed refractory block for strip heating furnaces



P 1968 H, G. HART ETAL 3,399,876

PREFORMED REFRACTORY BLOCK FOR STRIP HEATING FURNACES Filed Feb. 24, 1966 IYllllllllllllllllI! I III INVENTORS HOW4/PD 6. 1/4/97 .00 ALD F. 5706K l u ATTORNEY United States Patent lice 3,399,876 PREFORMED REFRACTORY BLOCK FOR STRIP HEATING FURNACES Howard G. Hart, Collinsville, and Donald F. Stock, Pittsburgh, Pa., assignors to Dresser Industries, Inc., Dallas, Tex., a corporation of Delaware Filed Feb. 24, 1966, Ser. No. 529,828 7 Claims. (Cl. 2o63) ABSTRACT OF THE DISCLOSURE A heat treating furnace for continuously annealing 3,399,876 Patented Sept. 3, 1968 tory bottoms in continuous strip annealing furnaces than was heretofore possible.

' Still another object of the invention is to provide an improved, preformed, slotted, refractory block for use at the discharge end of continuous metal strip annealing vessels.

Other objects of the invention, will, in part, be apparent hereinafter.

In order to more fully understand the nature and scope of the invention, reference should be had to the following detailed description and drawings in which:

FIG. 1 is a schematic elevation view in cross section of a typical continuous strip annealing vessel;

FIG. 2 is an isometric view of a preformed refractory block shown at the discharge end of the vessel of FIG. 1,

according to one embodiment of the invention; and

metal strip is generally an elongated vessel having a heating zone of about 60 feet or so in length and a width of about 6 to 8 feet and is so designed as to handle at a high rate of speed, continuous metal strip which may be as wide as 70 inches. The strip is usually coiled near the feed end of the furnace and passes over a series of rollers directing it to the feed end. The strip passes through the heating zone of the vessel, out of the discharge end and through the sub-structure on a series of rollers whereupon it is passed on for cooling or further treatment as desired and is ultimately recoiled.

The furnace, which generally is erected so that the feed and discharge ends are in vertical alignment, consists of an outer metal shell lined with refractory material. At the upper or feed end of the vessel therefractory material tapers to an opening compatible with'the metal strip being processed and overall furnace design; The lower or discharge end of the vessel must be supported on some sort of substructure which includes a provision for narrowing the discharge opening. with refractory material. The lower end, ordischarge end, may not be designed similarly to the upper end because of the disposition of the vessel.

In earlier'annealing vessels, after the sub-structure for the vessel was fabricated, a metallic frame was arranged within the substructure and a refractory material was cast in place within the frame, with an opening therein, to accommodate the metal strip passing through the hot zone. The remainder of the furnace was then built over the substructure with the heating chamber being in alignment with the slotted refractory bottom to provide a completely refractory lined vessel.

In processing the metal sheet at high rates of speed through the furnace, the sheet tends to buckle somewhat and at times a break occurs somewhere within the'heating chamber. If a break does occur in the strip, it strikes and piles up on the refractory bottom construction. This usually damages the refractory to an extent that it requires replacement. Such replacement entailed'shutting the furnace down until it cooled, entering the vessel, removing the refractory from the frame and casting another slotted bottom in place. Such replacement generally required a downtime of about 1 /2 to 2 days. With the construction of the present invention, which will be described subsequently, a maximum of about 2 hours is required for replacement of the refractory bottom.

Accordingly, it is an object of the present invention to provide an improved refractory bottom for a continuous metal strip heat treating furnace.

Another object of the invention is to provide a more economic and efficient means for replacement of refrac- FIG. 3 is an isometric view of a preformed refractory block according to another embodiment of the invention.

In accordance with the present invention, there is provided a metallurgical vessel for heat treating (i.e., annealing) continuous metal strip. The vessel consists of an elongated relatively narrow heating chamber containing an outer metal shell lined with refractory material. The vessel is provided with two open ends, one for feeding continuous metal strip to the chamber and the other for discharging the strip. At the discharge end of the vessel there is disposed a preformed refractory block characterized by having substantially parallel face surfaces. The block contains an elongated slot passing through the face surfaces in alignment with the open ends to admit passage of said metal strip therethrough.

Referring to FIG. 1, there is shown a typical annealing vessel 10. The vessel has an outer metal shell 12 which is lined with a suitable refractory material 14. The vessel contains an open feed end 16 where the refractory lining 14 tapers to a relatively narrow slit and a discharge end 18 which rests on a sub-structure 20 fabricated from an array of structural steel members.

The metal strip 22 is fed from its source over a series of rollers 24 shown above the vessel. The metal strip is directed through the slot at the feed end 16 and passes down through the furnace and heating chamber 26 at a relatively high rate of speed whereupon it passes through the slot 28 in a preformed refractory block 30 according to the present invention. After it passes through the refractory block it is directed by rollers 32 to a cooling source or other treating means as required by the specifications for processing the strip.

The preformed refractory block is actually disposed within the metal sub-structure of the vessel so that the upper face surface 34 of the block lies just below the open discharge end 18 of the vessel. The lower face 36 of the block is seated on a metal support, provided in the sub-structure for this purpose.

The refractory block 30 (as shown in FIG. 2), because of present furnace design is of generally rectangular configuration. The slot 28 passing through the face surfaces of the block is elongated along the length of the block to accommodate the passage of relatively thin but wide metal strip. In order to provide greater structural integrity for the block and longer life, it should be fabricated such that the outer periphery of the block and and contribute to the structural integrity and life of the block in service.

In order to facilitate placement and removal of the block from the support sub-structure 20 when necessary, it is preferred that the upper face surface of the block contain at least in each quadrant, a metallic projection 42, such as an eyelet. The projections may be welded to an inverted T-bar which is partially embedded in the refractory and coformed therewith. They also may be directly attached by means of a shaft to one or more of the metal rods.

Referring to FIG. 3, there is shown another embodiment of the invention. Here, instead of reinforcing bars embedded within the block, the block 30 contains a plurality'of heat dissipating metallic plates 44 secured to outer portions thereof. The plates serve to reinforce the block and to conduct heat around the block. It is preferred that a thermally insulating material (not shown) such as asbestos sheet, rockwool and the like be disposed between the plates and block.

It should be appreciated that other forms of reinforcing and heat dissipating means may be secured to the block without departing from the scope of the invention.

In the embodiment of FIG. 3, the metal projecting eyelets 46 may be directly attached, as by welding, to the outer plates.

As an example of the size of the block required in such vessels, in an annealing furnace capable of continuously handling steel strip up to about 66 inches wide, the block would measure about 6 /2 feet by 2 /2 feet by 11 inches. The slot in the block would measure 68 inches by 3% inches through the 11inch dimension in the block.

Accordingly, because of such size it can be appreciated why previous bottoms in annealing furnaces were cast in place. However, the structural design of the block of the present invention has made feasible its use in such furnaces in terms of longer life in service and rapid replacement when necessary.

The blocks of the present invention may be fabricated by methods well known in the art, for example, by slip casting, vibration casting or ramming a refractory material in a mold box containing a centrally located mandrel conforming to the desired slot or opening in the final shape. The reinforcing rods may be embedded in the shape during forming as may the anchors or shafts secured to the projecting metal members. In the embodiment of FIG. 3, the metal heat dissipating means may be .comolded with the block or they can be secured thereto with refractory adhesive in a manner well known in the art.

While the physical construction of the block itself facilitates rapid replacement as compared to previous constructions, and contributes largely to the service life of the shape, another consideration with regard to service life is the type of refractory material used to make the shapes. In the embodiment of FIG. 1, the shapes should have a relatively low thermal conductivity because of the tendency of the reinforcing rods to conduct heat through the shape and arelatively high hot strength to continuously resist the erosive conditions prevalent in processing the metal sheet material. For example, a material having a bulk density of between about 115 to 140 p.c.f. and a cold crushing strength (which is indicative of abrasion resistance) of about 1600 p.s.i. and higher at 1500 F., has been found satisfactory in most instances. Such blocks may be ables having these properties.

In the embodiment of FIG. 3, since much of the heat is dissipated around the block, higher thermal conductivities can be tolerated thus permitting the use of certain types of chrome ore and high alumina castables.

It is intended that the foregoing description and drawings be construed as illustrative and not in limitation of the invention.

Having thus described the invention in detail-and with sufficient particularity as to enable those skilled in the art to practice it, what is desired to have protected by Letters Patent is set forth in the following claims:

I claim: 7 w M 1. In a metallurgical vessel for heat treating continuous metal strip, which vessel consists of an elongated relatively narrow heating chamber containing an outer metal shell lined with refractory material, an open end for feeding continuous metal strip to the chamber and an open end for discharging said strip, the improvement comprising a preformed refractory block characterized by having substantially parallel uppermost and lowermost face sur-' faces, said uppermost face surface lying below theopen discharge and the lowermost face surface seated on a metal support, disposed at the open discharge end of the vessel, said refractory block having an elongated slot passing through the parallel face surface, said slot being elongated along the length of the block and in alignment with said open ends to permit passage of said metal strip therethrough, said block containing, on its uppermost face surface, projecting members for facilitating placement on and removal from said metal support.

2. The vessel of claim 1, in which the outer periphery of the block and the elongated slot are coaxial.

3. The vessel of claim 1, in which the refractory block has embedded therein a plurality of reinforcing rods.

4. The vessel of claim 1, in which the refractory block contains heat dissipating means secured to portions of its outer surfaces.

5. The vessel of claim 4, in which said heat dissipating means are in the form of metallic strips.

6. The vessel of claim 4, in which a thermally insulating material is disposed between the heat dissipating means and the refractory block.

7. The vessel of claim 4, in which projecting members for facilitating placement on and removal from the metal support are secured to the heat dissipating means.

References Cited UNITED STATES PATENTS 2,665,125 1/1954 Klug 263-3 2,668,701 2/1954 Dietrich 263-3 2,869,846 1/ 1959 Bloom.

2,998,966 9/ 1961 Knight.

3,110,484 11/ 1963 Anderson et all 266--3XR 3,182,982 5/1965 Ruff 2663 3,291,468 12/1966 Albertsen et a1 266-3 I FOREIGN PATENTS 1,192,410 4/1959 France.

I. SPENCER OVERHOLSER, Primary Examiner.

R. S. ANNEAR, Assistant Examiner.

made from fi reclay cast- 

